TheAlgorithms/Python · error · ValueError

area_parallelogram() only accepts non-negative values

Error message

area_parallelogram() only accepts non-negative values

What it means

area_parallelogram() raises this ValueError when base or height is negative. Both are physical measurements; the library enforces >= 0 before returning base * height. Note this function takes the perpendicular height, not a slanted side, so sign confusion here usually means bad input data rather than a geometry mistake.

Source

Thrown at maths/area.py:387

    >>> area_parallelogram(1.6, 2.6)
    4.16
    >>> area_parallelogram(0, 0)
    0
    >>> area_parallelogram(-1, -2)
    Traceback (most recent call last):
        ...
    ValueError: area_parallelogram() only accepts non-negative values
    >>> area_parallelogram(1, -2)
    Traceback (most recent call last):
        ...
    ValueError: area_parallelogram() only accepts non-negative values
    >>> area_parallelogram(-1, 2)
    Traceback (most recent call last):
        ...
    ValueError: area_parallelogram() only accepts non-negative values
    """
    if base < 0 or height < 0:
        raise ValueError("area_parallelogram() only accepts non-negative values")
    return base * height


def area_trapezium(base1: float, base2: float, height: float) -> float:
    """
    Calculate the area of a trapezium.

    >>> area_trapezium(10, 20, 30)
    450.0
    >>> area_trapezium(1.6, 2.6, 3.6)
    7.5600000000000005
    >>> area_trapezium(0, 0, 0)
    0.0
    >>> area_trapezium(-1, -2, -3)
    Traceback (most recent call last):
        ...
    ValueError: area_trapezium() only accepts non-negative values
    >>> area_trapezium(-1, 2, 3)

View on GitHub (pinned to f5988cc097)

Solutions

1. Validate base >= 0 and height >= 0 before the call; fix the negative source value.
2. Normalize signed projections with abs() when only magnitude matters.
3. Clean imported data to replace negative sentinels with missing-value markers.
4. Catch ValueError for a friendly application-level message.

Example fix

// before
area = area_parallelogram(base, height)  # height from projection, may be < 0

# after
area = area_parallelogram(base, abs(height))

if base < 0 or height < 0:
    raise ValueError(f'parallelogram base/height must be >= 0: {base}, {height}')
area = area_parallelogram(base, height)

def is_valid_parallelogram_dims(b: float, h: float) -> bool:
    return b >= 0 and h >= 0

try:
    area = area_parallelogram(base, height)
except ValueError as e:
    raise ValueError(f'invalid parallelogram input: {e}') from e

When it happens

Trigger: Calling area_parallelogram(base, height) with base < 0 or height < 0, e.g. area_parallelogram(-1, 2) or area_parallelogram(1, -2).

Common situations: Land-plot measurement imports with sign conventions; heights computed from coordinate projections that flip sign; -1 sentinels in legacy data files.

Related errors

• surface_area_cube() only accepts non-negative values
• surface_area_cuboid() only accepts non-negative values
• surface_area_sphere() only accepts non-negative values
• surface_area_hemisphere() only accepts non-negative values
• surface_area_cone() only accepts non-negative values

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/70decff27ee5481b. Report an issue: GitHub.